Among flat display devices, liquid crystal display (LCD) devices are widely used for notebook computers, monitors, aircraft, and other applications. LCDs have the advantages of high contrast ratio, good gray scale level, low power consumption, and good motion quality.
In particular, LCD technology may be applied to ultra-thin displays, such as wall-mountable televisions, because the LCD device has a thin profile. In addition, the LCD device is light in weight and has low power consumption; thus it may be used as a display device for a notebook computer which is driven by a battery. Also, the LCD device can be fabricated in a small size and used for a display of a mobile phone.
Generally, the LCD device includes an upper substrate of a color filter array substrate, a lower substrate of a thin film transistor array substrate, and a liquid crystal layer of a dielectric anisotropy. In this case, the lower and upper substrates are positioned in opposition to each other, and the liquid crystal layer is formed between the lower and upper substrates. A plurality of pixels are formed, each of which has a thin film transistor TFT. A voltage is applied to the corresponding pixel through a pixel-selection address line by switching the thin film transistor of the pixel region.
A light source (backlight) is provided to a rear surface of the LCD device. That is, the LCD device is formed in a transmitting mode, wherein the light emitted from the backlight is used to display images on a screen. In this case, a color filter layer of red (R), green (G) and blue (B) colors is provided to the LCD device.
The LCD device may also be used for a desktop monitor as well as for a notebook computer, in which case the color filter layer of the LCD device preferably has high luminosity and chromaticity.
Hereinafter, an LCD device according to the related art will be described with reference to the accompanying drawings.
FIG. 1 is a plan view of a general LCD device. FIG. 2 is a plan view of an LCD device according to the related art.
As shown in FIG. 1, a general LCD device includes a TFT array substrate 50 which is divided into a pixel area 52 for displaying images inside a dotted line of FIG. 1, and a non-pixel area 54 outside the dotted line of FIG. 1.
In the pixel area 52, there are a plurality of gate and data lines 61 and 62 crossing each other to define sub-pixels. Also, a thin film transistor TFT (not shown) is formed adjacent to a crossing of the gate and data lines 61 and 62. Each sub-pixel has a pixel electrode (not shown) which is electrically connected with a drain electrode of the thin film transistor. The images are displayed by switching the corresponding thin film transistor.
The non-pixel area 54 is provided with gate and data link lines 63 and 64 respectively extended from the gate and data lines 61 and 62. Each one end of the gate link lines 63 is connected with a gate drive IC 70, and each one end of the data link lines 64 is connected with a data drive IC 80.
The gate and data drive IC 70 and 80 are mounted by a tape automated bonding (TAB) method for connection with a printed circuit board (PCB) 90. On the PCB 90, there are a plurality of elements such as integrated circuits to generate various control signals and data signals for operation of the LCD device.
Although not shown, the color filter array substrate of the LCD device includes a color filter layer of red (R), green (G) and blue (B) color filter patterns, a black matrix layer for division of R, G and B color filter patterns and for light-shielding function, and a common electrode to apply a voltage to the liquid crystal cells.
After cutting the LCD device to a desired size, processes for edge grinding and polarizer attachment are performed. For the edge grinding process, the position of the LCD device is sensed by a charged-couple device (CCD) camera, and then a grinder grinds the edge of the LCD device. For the polarizer attachment process, after sensing the position of the LCD device with the CCD camera, a polarizer is attached to the LCD device.
To sense the precise position of the LCD device, the CCD camera may benefit from having an alignment mark. The alignment mark is formed corresponding to the region where the data and gate drive ICs is formed prior to the processes of edge grinding and polarizer attachment. For reference, the data and gate drive IC are connected with the LCD device after the processes of edge grinding and polarizer attachment.
Recently, a new model has been proposed, wherein the gate drive area is formed on the TFT array substrate and the space for mounting the gate drive IC is eliminated from the LCD device, thereby increasing the pixel area of the LCD device. In this case, the alignment mark may be hidden by the black matrix layer of the color filter array substrate.
In detail, as shown in FIG. 2, a PCB 190 is provided only corresponding to a data line part, and the PCB 190 is connected with a data drive IC 180. In this state, a gate drive area 170 is formed inside a non-pixel area 154 of the LCD device without the gate drive IC, thereby decreasing the non-pixel area in size corresponding to the region where the gate drive IC would be attached. Thus, an alignment mark corresponding to a related art gate drive IC is formed in the gate drive area 170.
In case of the LCD device having no gate drive IC, the space for mounting the gate drive IC is eliminated. That is, the alignment mark is hidden in the processes for edge grinding and polarizer attachment. In other words, the gate drive area 170 is overlapped with a color filter array substrate having a black matrix layer, and thus the alignment mark is hidden by the black matrix layer.
In the general LCD device, the alignment mark is formed in the portions including the gate and data drive ICs and having no black matrix layer so that it can be seen in the edge grinding and polarizer attachment processes, and therefore, such processes are performed without any problem. However, in case of the LCD device having no gate drive IC, the alignment mark formed in the TFT array substrate is hidden by the color filter array substrate, so that the CCD camera cannot sense the alignment mark. That is, the alignment mark is hidden by the black matrix layer formed at the edge of the color filter array substrate.